Biomarkers of susceptibility to chemical carcinogens: the example of non-Hodgkin lymphomas

Narrative review of occupational exposures and noncommunicable diseases

OBJECTIVE

Within the scope of the Exposome Project for Health and Occupational Research on applying the exposome concept to working life health, we aimed to provide a broad overview of the status of knowledge on occupational exposures and associated health effects across multiple noncommunicable diseases (NCDs) to help inform research priorities.

METHODS

We conducted a narrative review of occupational risk factors that can be considered to have "consistent evidence for an association," or where there is "limited/inadequate evidence for an association" for 6 NCD groups: nonmalignant respiratory diseases; neurodegenerative diseases; cardiovascular/metabolic diseases; mental disorders; musculoskeletal diseases; and cancer. The assessment was done in expert sessions, primarily based on systematic reviews, supplemented with narrative reviews, reports, and original studies. Subsequently, knowledge gaps were identified, e.g. based on missing information on exposure-response relationships, gender differences, critical time-windows, interactions, and inadequate study quality.

RESULTS

We identified over 200 occupational exposures with consistent or limited/inadequate evidence for associations with one or more of 60+ NCDs. Various exposures were identified as possible risk factors for multiple outcomes. Examples are diesel engine exhaust and cadmium, with consistent evidence for lung cancer, but limited/inadequate evidence for other cancer sites, respiratory, neurodegenerative, and cardiovascular diseases. Other examples are physically heavy work, shift work, and decision latitude/job control. For associations with limited/inadequate evidence, new studies are needed to confirm the association. For risk factors with consistent evidence, improvements in study design, exposure assessment, and case definition could lead to a better understanding of the association and help inform health-based threshold levels.

CONCLUSIONS

By providing an overview of knowledge gaps in the associations between occupational exposures and their health effects, our narrative review will help setting priorities in occupational health research. Future epidemiological studies should prioritize to include large sample sizes, assess exposures prior to disease onset, and quantify exposures. Potential sources of biases and confounding need to be identified and accounted for in both original studies and systematic reviews.

Brain-derived neurotrophic factor (BDNF): an effect biomarker of neurodevelopment in human biomonitoring programs

The present narrative review summarizes recent findings focusing on the role of brain-derived neurotrophic factor (BDNF) as a biomarker of effect for neurodevelopmental alterations during adolescence, based on health effects of exposure to environmental chemical pollutants. To this end, information was gathered from the PubMed database and the results obtained in the European project Human Biomonitoring for Europe (HBM4EU), in which BDNF was measured at two levels of biological organization: total BDNF protein (serum) and BDNF gene DNA methylation (whole blood) levels. The obtained information is organized as follows. First, human biomonitoring, biomarkers of effect and the current state of the art on neurodevelopmental alterations in the population are presented. Second, BDNF secretion and mechanisms of action are briefly explained. Third, previous studies using BDNF as an effect biomarker were consulted in PubMed database and summarized. Finally, the impact of bisphenol A (BPA), metals, and non-persistent pesticide metabolites on BDNF secretion patterns and its mediation role with behavioral outcomes are addressed and discussed. These findings were obtained from three pilot studies conducted in HBM4EU project. Published findings suggested that exposure to some chemical pollutants such as fine particle matter (PM), PFAS, heavy metals, bisphenols, and non-persistent pesticides may alter circulating BDNF levels in healthy population. Therefore, BDNF could be used as a valuable effect biomarker to investigate developmental neurotoxicity of some chemical pollutants.

Evaluation of the genotoxic and antigenotoxic effects of exopolysaccharide pullulan in human lymphocytes in vitro

Pullulan is a biocompatible and water-soluble exo-polysaccharide produced by primary strains of the fungus Aureobasidium pullulans. It is frequently used in the pharmaceutical and food industries. In this study, possible cytotoxic effect of pullulan was assessed using the MTT assay in the human breast cancer (MCF-7) cell line. Micronucleus (MN), micronucleus-FISH (MN-FISH), random amplified polymorphic DNA (RAPD-PCR), and comet assays were used to investigate genotoxic and antigenotoxic effects of pullulan against mitomycin C (MMC) (at MN assay) and hydrogen peroxide (at comet assay) in human lymphocytes. Antigenotoxicity was determined using two different applications: 1 h pretreatment and simultaneous treatment. In the MTT assay, pullulan significantly reduced the cell viability at 15.6-2000 μg/mL compared to the control. No significant alterations in MN rates were found in human lymphocytes treated with different concentrations of pullulan compared to the control. In contrast, co-treatment of pullulan and MMC decreased the frequency of MN in almost all the treatment concentrations and durations compared to the MMC. No significant change was observed in the frequency of the centromere-positive C + or negative C- MNi compared to the positive control. In comet assay, pullulan did not affect comet tail intensity compared to the negative control. On the contrary, pullulan in combination with H₂O₂ significantly decreased tail intensity at almost all the concentrations compared to the positive control. The changes occurring in RAPD-PCR profiles following pullulan treatments included an increase or decrease in band intensity and gain or loss of bands. These results indicate that exopolysaccharide Pullulan is not genotoxic; moreover, it possesses a protective effect against MMC and H₂O₂ induced genotoxicity. In breast cancer cells, pullulan induced cytotoxic/anti-proliferative effect.

Linking Environmental Exposures to Molecular Pathogenesis in Non-Hodgkin Lymphoma Subtypes

Non-Hodgkin lymphoma comprises a heterogeneous group of hematologic malignancies, with about 60 subtypes that arise via various pathogenetic mechanisms. Although establishing etiology for specific NHL subtypes has been historically difficult given their relative rarity, environmental exposures have been repeatedly implicated as risk factors across many subtypes. Large-scale epidemiologic investigations have pinpointed chemical exposures in particular, but causality has not been established, and the exact biologic mechanisms underpinning these associations are unclear. Here we review chemical exposures that have been associated with development of NHL subtypes and discuss their biologic plausibility based on current research.

Carcinogenicity assessment: Addressing the challenges of cancer and chemicals in the environment

Cancer is a key public health concern, being the second leading cause of worldwide morbidity and mortality after cardiovascular diseases. At the global level, cancer prevalence, incidence and mortality rates are increasing. These trends are not fully explained by a growing and ageing population: with marked regional and socioeconomic disparities, lifestyle factors, the resources dedicated to preventive medicine, and the occupational and environmental control of hazardous chemicals all playing a role. While it is difficult to establish the contribution of chemical exposure to the societal burden of cancer, a number of measures can be taken to better assess the carcinogenic properties of chemicals and manage their risks. This paper discusses how these measures can be informed not only by the traditional data streams of regulatory toxicology, but also by using new toxicological assessment methods, along with indicators of public health status based on biomonitoring. These diverse evidence streams have the potential to form the basis of an integrated and more effective approach to cancer prevention.

Metabolic Polymorphisms and Clinical Findings Related to Benzene Poisoning Detected in Exposed Brazilian Gas-Station Workers

Benzene is a ubiquitous environmental pollutant and an important industrial chemical present in both gasoline and motor vehicle emissions. Occupational human exposure to benzene occurs in the petrochemical and petroleum refining industries as well as in gas-station workers, where it can lead to benzene poisoning (BP), but the mechanisms of BP are not completely understood. In Brazil, a significant number of gas-station service workers are employed. The aim of the present study was to evaluate alterations related to BP and metabolic polymorphisms in gas-station service workers exposed to benzene in the city of Rio de Janeiro, Brazil. Occupational exposure was based on clinical findings related to BP, and metabolic polymorphisms in 114 Brazilian gas-station attendants. These workers were divided into No Clinical Findings (NCF) and Clinical Findings (CF) groups. Neutrophil and Mean Corpuscular Volume (MCV) showed a significant difference between the two study groups, and neutrophil has the greatest impact on the alterations suggestive of BP. The clinical findings revealed higher frequencies of symptoms in the CF group, although not all members presented statistical significance. The frequencies of alleles related to risk were higher in the CF group for GSTM1, GSTT1, CYP2E1 7632T > A, but lower for NQO1 and CYP2E1 1053C > T genotypes. Moreover, an association was found between GSTM1 null and alterations related to BP, but we did not observe any effects of other polymorphisms. Variations in benzene metabolizing genes may modify benzene toxicity and should be taken into consideration during risk assessment evaluations.

microRNA-218 suppresses the proliferation, invasion and promotes apoptosis of pancreatic cancer cells by targeting HMGB1

OBJECTIVE

To detect the expression profiles of microRNA-218 (miR-218) in human pancreatic cancer tissue (PCT) and cells and their effects on the biological features of human pancreatic cancer cell line PANC-1 and observe the effect of miR-218 on the expression of the target gene high mobility group box 1 (HMGB1), with an attempt to provide new treatment methods and strategies for pancreatic cancer.

METHODS

The expressions of miR-218 in PCT and normal pancreas tissue as well as in various pancreatic cancer cell lines including AsPC-1, BxPC-3, and PANC-1 were determined with quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The change of miR-218 expression in PANC-1 cells was detected using qRT-PCT after the transfection of miR-218 mimic for 48 h. Cell Counting Kit-8 (CCK-8) was applied for detecting the effect of miR-218 on the activity of PANC-1 cells. The effects of miR-218 on the proliferation and apoptosis of PANC-1 cells were analyzed using the flow cytometry. The effect of miR-218 on the migration of PANC-1 cells was detected using the Trans-well migration assay. The HMGB1 was found to be a target gene of miR-218 by luciferase reporter assay, and the effect of miR-218 on the expression of HMGB1 protein in cells were determined using Western blotting.

RESULTS

As shown by qRT-PCR, the expressions of miR-218 in PCT and in pancreatic cancer cell line significantly decreased when compared with the normal pancreatic tissue (NPT) (P<0.01). Compared with the control group, the miR-218 expression significantly increased in the PANC-1 group after the transfection of miR-218 mimic for 48 h (P<0.01). Growth curve showed that the cell viability significantly dropped after the overexpression of miR-218 in the PANC-1 cells for two days (P<0.05). Flow cytometry showed that the S-phase fraction significantly dropped after the overexpression of miR-218 (P<0.01) and the percentage of apoptotic cells significantly increased (P<0.01). As shown by the Trans-well migration assay, the enhanced miR-218 expression was associated with a significantly lower number of cells that passed through a Transwell chamber (P<0.01). Luciferase reporter assay showed that, compared with the control group, the relative luciferase activity significantly decreased in the miR-218 mimic group (P<0.01). As shown by the Western blotting, compared with the control group, the HMGB1 protein expression significantly decreased in the PANC-1 group after the transfection of miR-218 mimic for 48 h (P<0.01).

CONCLUSIONS

The miR-218 expression decreases in human PCT and cell lines. miR-218 can negatively regulate the HMGB1 protein expression and inhibit the proliferation and invasion of pancreatic cancer cells. A treatment strategy by enhancing the miR-218 expression may benefit the patients with pancreatic cancer.